1. Field of the Invention
The present invention relates to a buffering mechanism capable of properly absorbing shocks applied to a movable element of an actuator when the movable element arrives at a displacement end position.
2. Description of the Related Art
Actuators have been hitherto used, for example, to transport or position a workpiece. For example, in an air cylinder, the air in a cylinder chamber closed by a cylinder tube and a piston is compressed, for example, by a cushion ring or a cushion packing when the piston arrives at the displacement end position. The compressive force is adjusted by adjusting the flow rate of the air discharged from the cylinder chamber into the atmospheric air by means of a cushion valve composed of a flow rate control valve for performing a buffering function to absorb the shock applied to the piston.
However, when the buffering mechanism of the conventional technique is applied to an electric actuator in which a movable element is displaced linearly along an actuator body under the rotary driving action of a rotary driving source, it is impossible to use, for example, the cushion ring or the cushion packing. In the electric actuator, the air in an amount sufficient to perform the buffering function is not available.
Even if the cushion ring or the cushion packing is used, it is impossible to conveniently replace the cushion ring or the cushion packing when the durability is deteriorated due to the use for a long period of time.
A general object of the present invention is to provide a buffering mechanism which can be conveniently replaced and which is capable of properly performing the buffering function in a variety of actuators including, for example, electric actuators and fluid pressure-operated cylinders.
According to the present invention, a movable element of an actuator abuts against a displacement member when the movable element arrives at one or the other displacement end position. The displacement member is displaced together with the movable element, and thus the air in a compressing chamber is compressed. When the compressed air in the compressing chamber is discharged to the outside of an actuator body, the discharge flow rate of the compressed air is throttled by a discharge flow rate-adjusting member in a passage communicating with the outside of the actuator body. Therefore, the shock applied when the movable element arrives at the displacement end position is properly absorbed by the compressing action of the air in the compressing chamber pressed by the displacement member.
In this arrangement, for example, the displacement member and the discharge flow rate-adjusting member are provided in the block member, and the block member is detachably installed in the actuator body. Therefore, the buffering mechanism can be replaced conveniently.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.